Abstract
A low molecular weight serine protease from seeds of Citrullus colocynthis was purified to electrophoretic homogeneity with high level of catalytic efficiency (22,945 M−1 S−1). The enzyme was a monomer with molecular mass of 25 kDa estimated by SDS–PAGE. The enzyme was highly active over a pH range of 6.5–9.0 and temperature range of 20–80 °C, with maximum activity at pH 7.5 and at 50 °C. The Km and Kcat were 73 μg/mL and 67/s, respectively. The enzyme was strongly inhibited by PMSF, moderately by soybean trypsin inhibitor, indicating that the enzyme was a serine protease. The enzyme retained 86 and 73% of its activity in the presence of urea and DTT, respectively, and its activity was slightly enhanced in the presence of anionic detergent (SDS). Thus, the enzyme is a novel SDS-stable protease with high catalytic efficiency over wide ranges of pH and temperature which is commercially promising for various industrial applications.
Graphical abstract
![](/cms/asset/b79f8172-8698-4c0f-a320-77a7ffd2d20e/gnpl_a_1079909_uf0001_oc.jpg)
Acknowledgement
We are very grateful to Prof. Muhammad Iqbal Chaudry, director of HEJ-Research Institute of Chemistry, University of Karachi for allowing us to use their research facilities.
Disclosure statement
No potential conflict of interest was reported by the authors.